Eyeglasses injection moulding

In addition, our company has established cooperative relationships with plastic raw material suppliers, printing manufacturers, etc. to ensure the supply of raw materials and printing quality. Through our rich experience and perfect supply chain, our company can provide customers with high-quality customized eyeglasses injection moulding products to meet their specific needs. At the same time, we have 10 years of professional foreign trade service experience, understand the foreign trade process, and better serve our customers. For eyeglasses injection moulding products, we can make corresponding plastic parts, which is mainly done through injection molds.

The injection molding process for PC (polycarbonate) eyewear requires a balance of high transparency, impact resistance, dimensional accuracy, and surface quality. The following are key points:

1. Material Preparation

PC Characteristics:

High light transmittance (optical-grade PC, such as LEXAN™, is required), UV resistance, and high-temperature resistance (heat deflection temperature 130-140°C).

Because it is hygroscopic, it must be dried before injection molding (120°C for 4 hours, dew point ≤ -40°C) to prevent hydrolysis that may cause bubbles or silver streaks.

Additives: UV stabilizers (for outdoor use), antistatic agents, or hard coating materials (compatible with subsequent coatings).

2. Mold Design

High-quality cavity: The lens and frame areas require a mirror polish (Ra ≤ 0.05μm) to avoid flow marks or fogging.

Cold runner or hot runner:

Cold runner: Suitable for small batches, but gate marks must be controlled (for example, point gates should be located in non-optical areas).

Hot runner: Reduces waste, but prevents thermal decomposition (precisely controlled temperature within ±2°C).

Venting Design: Vents (depth 0.01-0.02mm) are provided on the parting surface and ejector pins to prevent trapped air and burning.

Temperature Control System: A mold temperature controller controls the mold temperature (80-110°C) to reduce warping or birefringence caused by internal stress.

3. Injection Molding Process Parameters

Temperature Control:

Barrel Temperature: Controlled in stages, rear section (240-260°C) → front section (280-310°C) to prevent overheating and degradation (PC melts at approximately 230°C).

Nozzle Temperature: Slightly lower than the front section (approximately 270-290°C) to prevent drooling.

Injection Stage:

High-speed, high-pressure filling (50-80% injection speed) ensures the reproduction of mirror-like details while avoiding spray marks (using a slow-entry gate).

Precise holding pressure (60-80% of injection pressure) and time (5-15 seconds) are crucial to prevent sink marks or internal stress caused by over-holding.

Cooling time: Long (40-50% of the cycle time) to ensure adequate solidification (PC has a slow cooling rate).

4. Common Defects and Countermeasures

Silver streaks/bubbles: Check material dryness, lower the melt temperature, or increase back pressure.

Internal stress cracking: Increase mold temperature, extend cooling time, or anneal (100-120°C for 1-2 hours).

Surface flow marks: Optimize the injection speed profile or adjust mold temperature uniformity.

5. Post-Processing and Inspection

Stress relief annealing: Heat treatment of high-precision frames or lenses to reduce subsequent deformation.

Surface treatment: Hard coating (such as hardening liquid spraying) and anti-reflective coating (clean environment required).

Full Inspection Items:

Optical properties (light transmittance, haze).

Dimensional tolerances (temple opening and closing angles, lens assembly gap).

Impact resistance testing (e.g., drop ball test, in accordance with EN166).

6. Special Process Considerations

Two-shot injection molding: If the frame and temples are of different colors/materials, a two-shot mold design is required.

Insert molding: When inserting metal hinges or logos, preheat the insert (80-100°C) to reduce thermal stress.

The injection molding process for PC (polycarbonate) lenses requires precision mold design, strict process parameter control, and post-processing to ensure that optical properties (e.g., transparency, refractive index) and mechanical properties (e.g., impact resistance, abrasion resistance) meet standards. The detailed process flow is as follows:

1. Raw Material Pretreatment

Drying

PC is highly hygroscopic and requires drying at 120°C for 4-6 hours (adjusted depending on particle size and humidity) to a moisture content of ≤0.02%.

Use a dehumidifying dryer to prevent secondary moisture absorption (recommended dew point ≤ -40°C).

Color matching (optional)

If dyeing is required, optical grade masterbatch should be used to avoid impurities affecting the transmittance.

2. Injection molding stage

(1) Melt plasticization

Temperature control

Barrel segment heating: rear section (240-260℃) → middle section (270-290℃) → front section (280-320℃) to avoid local overheating and PC degradation.

Screw speed ≤80 rpm to reduce molecular chain breakage caused by shear heat.

(2) Injection molding

Multi-stage injection

First stage: high-speed filling (to prevent cold material), injection speed 50-80% of the maximum speed.

Second stage: reduce speed to 20-30% to reduce weld marks and internal stress.

Pressure: injection pressure 80-120MPa, holding pressure 40-60MPa (to maintain shrinkage).

Mold temperature control

Mold temperature is 80-110℃, using oil temperature controller or high-precision mold temperature controller, with temperature difference within ±1℃.

(3) Holding pressure and cooling

Holding pressure time: 10-30 seconds (adjusted according to wall thickness, usually estimated as 1mm thickness ≈ 1 second).

Cooling time: more than 50% of the total cycle (usually 20-60 seconds), to ensure that the lens is fully cured.

(4) Demolding

The ejection system needs to be stable (such as pneumatic ejection or servo ejector) to avoid whitening or scratches.

The demoulding slope is ≥1°, and a release agent is sprayed if necessary (it must not affect subsequent coating).

3. Post-processing process

(1) Annealing treatment

Conditions: Anneal in an oven at 110-130℃ for 2-4 hours, and slowly cool to room temperature.

Purpose: To eliminate internal stress and reduce subsequent deformation or optical distortion.

(2) Surface treatment

Hard coating: Vacuum coating (such as SiO₂, TiN) is used to increase surface hardness (up to 4H or above).

Anti-reflective coating: Multi-layer coating (MgF₂, etc.) reduces glare and increases light transmittance to over 99%.

(3) Cleaning and inspection

Ultrasonic cleaning is used to remove release agents and dust, and a dust-free workshop environment is used.

100% inspection: transmittance (spectrophotometer), surface defects (automatic optical inspection (AOI), dimensional accuracy (three-dimensional measurement)eyeglasses injectionmoulding

We are a eyeglasses injection moulding manufacturer, providing high-quality eyeglasses injection moulding manufacturing. As long as you want to customize/develop eyeglasses injection moulding products, you can find us. We have professional injection mold design and mature manufacturing technology, providing you with one-stop service, from product design-mold making-product production-product packaging-product transportation, we can help you in every link. As long as you come to us, we will provide you with the ultimate service and satisfy you in terms of product quality, production time, information dialogue, etc.

Plastic Injection Mould making

Plastic molding specifications

Mold design:

Transaction process:

Mold testing:

Product packaging

Factory

We are Custom Plastic Mold factory. Our factory is plastic injection mold maker. we has 17 years of experience in professional custom plastic mold and 10 years of foreign trade experience. We are custom Plastic Mold supplier. We can provide custom Plastic Mold service. Our factory can make the Injection molded plastic parts, and the quality of the products will satisfy you.

We have more than 50 high-end machines and hundreds of engineers and designers. We can provide one-stop service, from product design - mold making - product production - product packaging - transportation. We have a complete production chain. We can meet all your requirements.

Services we provide:

Professional custom mold service, Plastic mold design and manufacturing .plastic product production, product design, mold design, blow mold customization, rotational mold customization, die-casting mold customization. 3D printing services, CNC manufacturing services, product packaging, customized packaging, shipping services.

We always adhere to the principles of quality first and time first. While providing customers with the highest quality products, try to maximize the production efficiency and shorten production time. We are proud to tell every customer that our company has not lost any customer since its establishment.If there is a problem with the product, we will seek a solution actively and take responsibility to the end.

FAQ

Q1: Are you trading company or manufacturer ?

A: We are manufacturers.

Q2. When can I get the quotation?

A: We usually quote within 2 days after we get your inquiry.

If you are very urgent, please call us or tell us in your email so that we can quote for you first.

Q3. How long is the lead-time for mold?

A: It all depends on the products' size and complexity. Normally, the lead time is 25 days.

Q4. I have no 3D drawing, how should I start the new project?

A: You can supply us a molding sample, we will help you finish the 3D drawing design.

Q5. Before shipment, how to make sure the products quality?

A: If you don't come to our factory and also don't have the third party for inspection, we will be as your inspection worker.

We will supply you a video for production process detail include process report, products size structure and surface detail, packing detail and so on.

Q6. What is your payment terms?

A: Mold Payment: 40% deposit by T/T in advance, 30% second mold payment before sending out the first trial samples, 30% mold balance after you agree the final samples.

B:Production Payment: 50% deposit in advance, 50% before sending out the final goods.

Q7: How do you make our business long-term and good relationship?

A:1. We keep good quality and competitive price to ensure our customers benefit for best quality products.

2. We respect every customer as our friend and we sincerely do business and make friends with them, no matter where they come from.